[llvm] r216586 - Reland r216439 215441, majnemer has a real fix for PR20771.

[Nico Weber]

Author: nico
Date: Wed Aug 27 15:06:19 2014
New Revision: 216586

URL: http://llvm.org/viewvc/llvm-project?rev=216586&view=rev
Log:
Reland r216439 215441, majnemer has a real fix for PR20771.

Added:
    llvm/trunk/test/Transforms/InstSimplify/gep.ll
      - copied unchanged from r216581, llvm/trunk/test/Transforms/InstSimplify/gep.ll
Modified:
    llvm/trunk/include/llvm/IR/PatternMatch.h
    llvm/trunk/lib/Analysis/InstructionSimplify.cpp

Modified: llvm/trunk/include/llvm/IR/PatternMatch.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/PatternMatch.h?rev=216586&r1=216585&r2=216586&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/PatternMatch.h (original)
+++ llvm/trunk/include/llvm/IR/PatternMatch.h Wed Aug 27 15:06:19 2014
@@ -362,6 +362,29 @@ struct bind_const_intval_ty {
   }
 };
 
+/// Match a specified integer value or vector of all elements of that value.
+struct specific_intval {
+  uint64_t Val;
+  specific_intval(uint64_t V) : Val(V) {}
+
+  template<typename ITy>
+  bool match(ITy *V) {
+    ConstantInt *CI = dyn_cast<ConstantInt>(V);
+    if (!CI && V->getType()->isVectorTy())
+      if (const auto *C = dyn_cast<Constant>(V))
+        CI = dyn_cast_or_null<ConstantInt>(C->getSplatValue());
+
+    if (CI && CI->getBitWidth() <= 64)
+      return CI->getZExtValue() == Val;
+
+    return false;
+  }
+};
+
+/// Match a specific integer value or vector with all elements equal to the
+/// value.
+inline specific_intval m_SpecificInt(uint64_t V) { return specific_intval(V); }
+
 /// m_ConstantInt - Match a ConstantInt and bind to its value.  This does not
 /// match ConstantInts wider than 64-bits.
 inline bind_const_intval_ty m_ConstantInt(uint64_t &V) { return V; }

Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=216586&r1=216585&r2=216586&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
+++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Wed Aug 27 15:06:19 2014
@@ -2799,29 +2799,71 @@ Value *llvm::SimplifySelectInst(Value *C
 static Value *SimplifyGEPInst(ArrayRef<Value *> Ops, const Query &Q, unsigned) {
   // The type of the GEP pointer operand.
   PointerType *PtrTy = cast<PointerType>(Ops[0]->getType()->getScalarType());
+  unsigned AS = PtrTy->getAddressSpace();
 
   // getelementptr P -> P.
   if (Ops.size() == 1)
     return Ops[0];
 
-  if (isa<UndefValue>(Ops[0])) {
-    // Compute the (pointer) type returned by the GEP instruction.
-    Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, Ops.slice(1));
-    Type *GEPTy = PointerType::get(LastType, PtrTy->getAddressSpace());
-    if (VectorType *VT = dyn_cast<VectorType>(Ops[0]->getType()))
-      GEPTy = VectorType::get(GEPTy, VT->getNumElements());
+  // Compute the (pointer) type returned by the GEP instruction.
+  Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, Ops.slice(1));
+  Type *GEPTy = PointerType::get(LastType, AS);
+  if (VectorType *VT = dyn_cast<VectorType>(Ops[0]->getType()))
+    GEPTy = VectorType::get(GEPTy, VT->getNumElements());
+
+  if (isa<UndefValue>(Ops[0]))
     return UndefValue::get(GEPTy);
-  }
 
   if (Ops.size() == 2) {
     // getelementptr P, 0 -> P.
     if (match(Ops[1], m_Zero()))
       return Ops[0];
-    // getelementptr P, N -> P if P points to a type of zero size.
-    if (Q.DL) {
-      Type *Ty = PtrTy->getElementType();
-      if (Ty->isSized() && Q.DL->getTypeAllocSize(Ty) == 0)
+
+    Type *Ty = PtrTy->getElementType();
+    if (Q.DL && Ty->isSized()) {
+      Value *P;
+      uint64_t C;
+      uint64_t TyAllocSize = Q.DL->getTypeAllocSize(Ty);
+      // getelementptr P, N -> P if P points to a type of zero size.
+      if (TyAllocSize == 0)
         return Ops[0];
+
+      // The following transforms are only safe if the ptrtoint cast
+      // doesn't truncate the pointers.
+      if (Ops[1]->getType()->getScalarSizeInBits() ==
+          Q.DL->getPointerSizeInBits(AS)) {
+        auto PtrToIntOrZero = [GEPTy](Value *P) -> Value * {
+          if (match(P, m_Zero()))
+            return Constant::getNullValue(GEPTy);
+          Value *Temp;
+          if (match(P, m_PtrToInt(m_Value(Temp))))
+            return Temp;
+          return nullptr;
+        };
+
+        // getelementptr V, (sub P, V) -> P if P points to a type of size 1.
+        if (TyAllocSize == 1 &&
+            match(Ops[1], m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0])))))
+          if (Value *R = PtrToIntOrZero(P))
+            return R;
+
+        // getelementptr V, (ashr (sub P, V), C) -> Q
+        // if P points to a type of size 1 << C.
+        if (match(Ops[1],
+                  m_AShr(m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0]))),
+                         m_ConstantInt(C))) &&
+            TyAllocSize == 1ULL << C)
+          if (Value *R = PtrToIntOrZero(P))
+            return R;
+
+        // getelementptr V, (sdiv (sub P, V), C) -> Q
+        // if P points to a type of size C.
+        if (match(Ops[1],
+                  m_SDiv(m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0]))),
+                         m_SpecificInt(TyAllocSize))))
+          if (Value *R = PtrToIntOrZero(P))
+            return R;
+      }
     }
   }